How to Remove an Old Corroded Galvanized Drain Pipe

by Chris Deziel

The most efficient way to remove a galvanized pipe from a drain line is to cut it off.

Plumbers don't recommend galvanized steel pipes for residential water or drain lines because they corrode from the inside. The corrosion produces deposits on the inside of the pipe that grow and eventually block water flow which, in a drain, means sluggish draining. You could disassemble the drain pipes back to the corroded one by unscrewing them from each other, but the fact that the threads are usually locked together makes that procedure impractical. In practice, it's easier to simply cut the damaged pipe and unscrew both ends from the fittings.

1

Block the drain so you don't have to deal with water and debris flowing through the pipe while you're working on it. If the drain is hooked up to a sink, turn off the shutoff valves for the faucet so no one will inadvertently turn on the faucet while the drain is disconnected.

2

Insert a metal-cutting blade onto a reciprocating saw, and make a straight cut through the drain pipe near its center. After completing the cut, make a second one about an inch away from it and remove a 1-inch section of pipe.

3

Unscrew each end of the pipe from the fitting with a pipe wrench. The pipe probably won't turn easily, so hold the fitting steady with a second pipe wrench, so you can apply as much force as possible to the pipe without damaging the rest of the drain line.

4

Loosen the threads with spray lubricant if you can't get the pipe to turn. Spray the lubricant into the threads and give it about five minutes to soak in before you try turning the pipe. If it doesn't work the first time, spray more.

5

Lubricate the threads with a plumber's candle if spray lubricant doesn't work. Heat the joint with a torch until it is hot enough to melt the wax from the candle. Hold the candle next to the joint and allow the wax to wick into the threads. Once you've done this, the pipe should turn more easily.

Things You Will Need

Reciprocating saw

Metal-cutting blade

2 pipe wrenches

Spray lubricant

Plumber's candle

Torch

Tip

Replace the pipe with two smaller pipes that have a combined length equal to it. Join the two replacement pipes with a union.

Clean the threads of the fittings from which you remove the ends of the pipe with a small brush, such as a toothbrush, before screwing on new pipes.

About the Author

A love of fundamental mysteries led Chris Deziel to obtain a bachelor's degree in physics and a master's degree in humanities. A prolific carpenter, home renovator and furniture restorer, Deziel has been active in the building and home design trades since 1975. As a landscape builder, he helped establish two gardening companies.

Photo Credits

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